The present invention, in some embodiments thereof, relates to magnetic resonance imaging (MRI) and, more particularly, but not exclusively, to a method and system for presenting and optionally characterizing cortical structures.
The cortex is organized in a laminar arrangement of neuronal morphology (cortical layers), with six distinct layers of cellular arrangement having similar composition throughout the cortex but differ in width between regions. This morphological, cyto-architectonic feature of the cortex is the basis for its parcellation into neuro-anatomical regions. The most common reference of such parcellation is the Brodmann's map of 47 cortical regions introduced in 1907. Other cyto-architectonic based cortical segmentations exist, but Brodmann's parcellation is the most common brain localization system in neuroscience today.
The six cortical layers possess neurons with different composition and morphology. The density and shape of neurons greatly varies along the cortex; from scattered pattern of small neurons at the first layer (molecular layer) to dense pattern of large and small neurons and neuronal fibers at the deeper layers (pyramidal and multiform layers). In addition, each layer has characteristics connections with other layers or brain regions. For example, the inner-granular layer (layer IV), connects with the thalamus and other inter-hemispheric cortical regions.
The cortical layers are formed during development when neurons migrate to the cortex from the ventricular zone. The layers are formed such that the deepest layers are formed by newer neurons. The formation of the layers is synchronized with the formation of other brain structures that the specific layers connect with.
Several attempts have been made to identify brain structures in vivo. A quantitative comparison of the lamination patterns observed in high-resolution magnetic resonance (MR) images of the human cerebral cortex with both myelo- and cytoarchitectonic patterns has been reported in Eickhoff et al., 2005, “High-Resolution MRI Reflects Myeloarchitecture and Cytoarchitecture of Human Cerebral Cortex,” Human Brain Mapping 24:206-215. This study has shown that the cortical lamination pattern visible on T1-weighted MR images reflects myelo- and cytoarchitecture.
U.S. Pat. No. 5,185,809 discloses a computerized technique for volumetric measurements of selected regions of the brain. The outline of a selected region in a slice of MR data is automatically determined and a volumetric measurement is made by determining for each slice the areas within the outline and summing the product of the areas and their respective thicknesses for all the slices.
U.S. Pat. No. 6,490,472 discloses a technique for producing an indication of the presence of Alzheimer's disease by measuring the functional connectivity at different locations in the brain. The technique involves measurement of functional connectivity of the brain between a plurality of locations in the hippocampus region of the brain that are affected by the disease. The measurement is made by acquiring MR images from a plurality of locations using an MRI system which includes an inversion recovery preparation sequence. The presence of the disease is determined when the measured connectivity is below a preset level.
Additional background art includes U.S. Pat. No. 5,588,431 and U.S. Published Application No. 20040162483.